Method and force-limiting handle mechanism for a surgical instrument

ABSTRACT

A safety handle assembly for use with a surgical instrument having an operative distal end portion is disclosed. The handle assembly includes a handle housing and a drive element movably mounted within the handle housing and connected to an associated operative distal end portion. A drive assembly is positioned within the handle housing and is engageable with the drive element to move the drive element within the handle housing. An actuator is movably mounted on the handle housing and an adjustable force-limiting mechanism is interposed between the drive assembly and the actuator. A force-limiting mechanism releasably connects the actuator to the drive assembly. The force-limiting mechanism is adjustable to preset the force at which the actuator separates or breaks away from the drive assembly.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a Divisional Application claiming the benefitof and priority to U.S. patent application Ser. No. 11/543,424, filed onOct. 5, 2006, the entire content of which is incorporated herein byreference.

BACKGROUND

Technical Field

The present disclosure relates to a method and handle assembly for usewith a surgical instrument. More particularly, the present disclosurerelates to a method and handle assembly incorporating a force-limitinghandle mechanism for use with a surgical instrument having a distal endeffector.

Background of Related Art

Various instruments are used during surgical procedures to manipulatetissue. Some of these instruments incorporate a handle assembly which isprovided to transmit a force to an end effector applied to tissue. Forexample, some surgical instruments may be provided with a pair of jawson the distal end to grasp or cut various tissues. Operation of thehandle assembly opens and closes the jaws by transmitting a force from atrigger mechanism associated with the handle assembly to the jaws andthus to the tissue. Other types of surgical instruments may be providedwith fastener applying end effectors which are configured to applystaples, clips, or other fasteners to tissue. Operation of the handleassemblies associated with these types of surgical instruments functionsto drive staples through and/or into tissue or compress surgical clipsabout the tissue by transmitting a force from the handle assembly to thestaple or clip applying end effector.

During the performance of certain surgical procedures with the abovedescribed surgical instruments, application and transmission of forcefrom the handle assemblies to the end effectors may ultimately result inexcessive damage to the tissues being operated on. For example, whengrasping instruments are utilized to manipulate tissue, excessive forceapplied to tissue may inadvertently cause damage to tissue.

In addition to the potential for damaging tissue due to excessive forcetransmitted from the handle assembly to the end effector of a surgicalinstrument, damage may also occur to the instrument itself. This mayoccur where the tissue being operated on is sufficiently stiff or hardsuch that it cannot be compressed or cut by the surgical instrument.Additionally, certain hard tissues may not be able to be penetrated bythe amount of force applied to fasteners in situations where stapling oftissue is desired. Similarly, instruments may not be able to completelycompress the tissues where compression of tissues is required during theapplication of surgical clips. Furthermore, many surgical instrumentsutilize replaceable or disposable cartridge assemblies to apply multipleclips or staples to tissue. Improper positioning of the cartridgeassemblies on the surgical instrument, or malfunction of the cartridgeassemblies themselves, may result in a resistance of the surgicalinstrument to application of pressure on the trigger of a handleassembly thereby causing damage to the surgical instrument itself. Thismay also occur where the cartridge assembly is devoid of fasteners andthe surgeon attempts to continue or reuse the surgical instrument.

Thus, a handle assembly for use with a surgical instrument whichincorporates a mechanism to limit the amount of force transmitted fromthe handle assembly to the end effectors to prevent damage to tissue maybe useful. Furthermore, a handle assembly for use with a surgicalinstrument which is capable of limiting the amount of force transmittedto an end effector to prevent damage to the surgical instrument itselfmay also be useful.

SUMMARY

There is disclosed a handle assembly having an adjustable force-limitingmechanism for use with a surgical instrument having an operative distalend portion. The handle assembly generally includes a handle housing anda drive element movably mounted within the handle housing and connectedto an operative distal end portion. A drive assembly is positionedwithin the handle housing and is engageable with the drive element tomove the drive element within the handle housing. An actuator is movablymounted on the handle housing.

A force-limiting mechanism is interposed between the drive assembly andthe actuator such that the force-limiting mechanism releasably connectsthe actuator to the drive assembly. The force-limiting mechanismincludes a connecting rod having a first end attached to the driveassembly and a second end mounted within the actuator. Theforce-limiting mechanism includes a spring positioned within theactuator and adjacent the second end of the connecting rod. Theforce-limiting mechanism also includes an adjustment screw positionedwithin the actuator and engageable with the spring to vary the forcewithin the spring.

The connecting rod has a protrusion and the drive assembly includes acut out portion releasably engageable with the protrusion on theconnecting rod. In one embodiment, the drive assembly includes an uppercarrier and a lower carrier. The upper carrier is connected to a firstend of the connecting rod. The lower carrier includes the cut outportion of the drive assembly and is engageable with the protrusion onthe connecting rod. In one embodiment, the connecting rod has a ramp forsupporting the portion of the lower carrier including the cut outportion when the cut out portion is disengaged from the protrusions onthe connecting rod.

The lower carrier is rotatably mounted on the handle housing and definesa first axis with a pivot point on the upper carrier. The connecting roddefines a second axis with a connection point on the upper carrier. Thefirst and second axes are substantially parallel when the protrusionsare engaged with the cut outs. The first and second axes aresubstantially nonparallel when the protrusions are disengaged from thecut outs. In one embodiment, the lower carrier has at least one flexiblearm containing the cut out. The flexible armed is flexible outwardlyrelative to the lower carrier when the protrusion is disengaged from thecut out to disconnect the drive assembly from the connecting rod. Theconnecting rod includes a ramp for support of the flexible arm when theprotrusion is disconnected from the cut out.

There is also disclosed a handle assembly for use with a surgicalinstrument having an operative distal end portion. The handle assemblygenerally includes a handle housing and a rack movably mounted withinthe handle housing and connected to an operative distal end portion. Adrive assembly is positioned within the handle housing and includes apawl engageable with the rack. A trigger is pivotally mounted on thehandle housing and an adjustable force-limiting mechanism is releasablyattached to a portion of the drive assembly. A portion of the adjustableforce-limiting mechanism is mounted for movement within the trigger. Theadjustable force-limiting mechanism releasably connects the trigger tothe drive assembly.

The adjustable force-limiting mechanism includes a connecting rod havinga first end connected to a portion of the drive assembly and a secondend movably mounted within the trigger. The adjustable force-limitingmechanism also includes a spring mounted within the trigger such thatthe first end of the spring is engageable with the second end of theconnecting rod. An adjustment screw is mounted within the trigger suchthat rotation of the adjustment screw alters the pressure within thespring. In one embodiment, the adjustable force-limiting mechanismincludes a bushing mounted within the trigger and positioned between thespring and the adjustment screw.

In an embodiment, the force-limiting mechanism includes a carriageattached to the actuator. It is envisioned that the handle assemblyincludes a pawl pivotably connected to the carriage. The force-limitingmechanism includes a plunger slidably connected to the actuator. Theplunger is slidably disposed at least partially in the actuator. In anembodiment, at least one spring is disposed between the plunger and theactuator. It is envisioned that the carriage has an angled surface forengaging the plunger. The plunger has an angled face for engaging theangled surface of the carriage. The angled surface and the angled faceare arranged so that the carriage depresses the plunger. The plunger isbiased toward the carriage with a predetermined biasing force.

There is also disclosed a method of controlling the amount of forceapplied to an end effector by handle assembly which includes providing ahandle assembly having a handle housing and a rack movably mountedwithin the handle housing. A drive assembly is mounted within the handlehousing and is engageable with a rack. A trigger is pivotally mountedwithin the handle housing and a force-limiting mechanism is interposedbetween the drive assembly and the trigger such that the force-limitingmechanism releasably connects the trigger to the drive assembly. Atleast a portion of the force-limiting mechanism is urged into engagementwith the drive assembly by a predetermined force. The force-limitingmechanism is released from the drive assembly in response to apredetermined amount of force applied to the rack. The portion of theforce-limiting mechanism urged into engagement with the drive assemblyincludes a spring biased plunger which is configured to engage the driveassembly.

DESCRIPTION OF THE DRAWINGS

An embodiment of the presently disclosed handle assembly incorporatingan adjustable force-limiting mechanism is disclosed herein withreference to the drawings, wherein:

FIG. 1 is a perspective view of the handle assembly with half of ahandle housing removed;

FIG. 2 is a perspective view of the handle assembly with the partsseparated;

FIG. 3 is a side view of the handle assembly with half of the handlehousing removed and in an initial position;

FIG. 4 is a perspective view of the handle assembly during initialdeactivation of a force-limiting mechanism associated with the handleassembly;

FIG. 5 is an end view of the force-limiting mechanism components of thehandle assembly during disengagement of the force-limiting mechanismfrom an associated drive assembly;

FIG. 6 is a perspective view of the handle assembly with theforce-limiting mechanism components disconnected from the driveassembly;

FIG. 7 is a perspective view of a handle assembly incorporating aforce-limiting trigger switch, with half of a handle housing removed;

FIG. 8 is perspective view, with parts separated, of the handle assemblyof FIG. 7,

FIG. 9 is side view of the handle assembly, with half of the handlehousing removed, in an initial, pre-firing condition;

FIG. 10 is an enlarged side view of the handle assembly in an initial,actuated condition;

FIG. 11 is an enlarged side view of the handle assembly during initialactuation and encountering an overload condition; and

FIG. 12 is an enlarged side view of the handle assembly during anoverload condition with a trigger disengaged from drive components ofthe handle assembly.

DETAILED DESCRIPTION OF EMBODIMENTS

An embodiment of the presently disclosed handle assembly incorporating aforce-limiting handle mechanism will now be described in detail withreference to the drawings wherein like numerals designate identical orcorresponding elements in each of the several views. As is common in theart, the term “proximal” refers to that part or component closer to theuser or operator, e.g., surgeon or physician, while the term “distal”refers to that part or component farther away from the user.

Referring initially to FIG. 1, there is disclosed a handle assembly 10for use with a surgical instrument. Handle assembly 10 incorporates anadjustable force-limiting mechanism 30 (e.g., clutch) to preventexcessive force applied to tissue and to prevent damage to handleassembly 10 itself in the event of an overload condition present at anassociated end effector. Handle assembly 10 is particularly suitable foruse in surgical instruments incorporating end effectors, such as clip orstaple applying apparatus, in their distal end portions. Handle assembly10 generally includes a handle housing 12 having an elongate drivingrack 14 mounted for longitudinal movement within handle housing 12.While handle assembly 10 is illustrated with only one half of handlehousing 12 visible, a complete and fully functional handle assembly 10includes two halves of handle housing 12. Handle assembly 10additionally includes an actuator or trigger 16 movably mounted onhandle housing 12. Actuation of trigger 16 causes driving rack 14 tomove longitudinally within handle housing 12.

Handle housing 12 is additionally provided with a journaled nose portion18 for rotatable support of the distal end portion of a surgicalinstrument. This allows end effectors associated with the distal endportion of the surgical instrument to be rotated relative to handleassembly 10.

To move driving rack 14, handle assembly 10 includes a drive assembly 20positioned between driving rack 14 and trigger 16. Drive assembly 20transfers motion applied to trigger 16 by a portion of an operator'shand to driving rack 14 to translate driving rack 14 longitudinallywithin handle housing 12 and thus actuate an associated end effector.Drive assembly 20 includes an upper carrier 22 and a pawl 24 for movingrack 14 within handle housing 12 in response to actuation of trigger 16in a manner described in more detail hereinbelow. Specifically, pawl 24is provided with a distal lip 26 which is configured to engage teeth 28formed in rack 14. Teeth 28 are oriented such that distal lip 26 canengage teeth 28 and move driving rack 14 distally within handle housing12 when pawl 24 is moved in the distal direction and disengage fromdriving rack 14 as pawl 24 is drawn in a proximal direction relative todriving rack 14.

As noted hereinabove, handle assembly 10 includes adjustableforce-limiting mechanism 30 which is provided to disengage trigger 16from drive assembly 20, and thus from driving rack 14, whenforce-limiting mechanism 30 encounters a predetermined amount of forcebetween drive assembly 20 and trigger 16. This may occur in a situationwhere an end effector encounters sufficiently stiff or tough materialssuch that continued actuation of the surgical instrument results indamage to the surgical instrument or tissues. Additionally, theexcessive force condition may occur in the event of damage to theassociated end effectors thereby preventing driving rack 14 fromtranslating longitudinally within handle housing 12.

In a particular application, the limit of the excessive force conditionmay be preset during configuration of handle assembly 10 such that anend effector associated with handle assembly 10 may only apply a forceup to a predetermined force to the tissue being operated upon. This maybe desirable when the associated end effector is configured to applysurgical clips or staples to tissue. Once the predetermined or presetforce has been reached, force-limiting mechanism 30 enables trigger 16to be disengaged from drive assembly 20 thereby preventing an excess ofamount of force being applied to the tissues.

Force-limiting mechanism 30 generally includes a lower carrier 32, whichalso forms a part of drive assembly 20, and a connecting rod 34engageable with lower carrier 32 and upper carrier 22. Adjustableforce-limiting mechanism 30 additionally includes a pressure spring 36positioned within a pocket 38 in trigger 16. In an embodiment, pressurespring 36 supplies a progressive force bias to trigger 16 whenforce-limiting mechanism 30 is engaged to limit or prevent a large forcedisparity and/or acceleration of trigger 16 to its user. Pressure spring36 also applies pressure to connecting rod 34 and is adjustable by meansof an adjustment screw 40 located within trigger 16. A bushing 42 isalso positioned within trigger 16 to support pressure spring 36 withintrigger pocket 38. Bushing 42 has a threaded interior for receipt ofadjustment screw 40 such that rotation of adjustment screw 40 movesbushing 42 to increase or decrease the pressure in pressure spring 36.Trigger 16 may include a window 44 for remote access to adjustment screw40 to adjust the pressure applied by pressure spring 36 on connectingrod 34.

As noted above, lower carrier 32 forms a portion of both drive assembly20 and adjustable force-limiting mechanism 30. Lower carrier 32 allowsdrive assembly 20 to be disconnected from connecting rod 34 and thusfrom trigger 16. Lower carrier 32 includes one or more cut outs 46 whichcooperate with corresponding one or more protrusions 48 formed onconnecting rod 34 to maintain lower carrier 32 in engagement withconnecting rod 34. During an excessive pressure condition, cut outs 46allow lower carrier 32 to disengage from connecting rod 34 by flaringoutwardly away from protrusions 48 in a manner described in more detailhereinbelow. Ramps 50 are provided on connecting rod 34 to maintainlower carrier 32 in a flared or splayed condition after carrier 32 hasbeen released from connecting rod 34. By maintaining lower carrier 32 inthe flared condition, carrier 32 can reengage connecting rod 34.Additionally, ramps 50 facilitate reengagement of protrusion 48 intocarrier 32 when trigger 16 is at least partially released.

As discussed, rack 14 is mounted for longitudinal movement within handlehousing 12. Rack 14 includes a rack lip 52 which rides along a housingrail 54 formed in handle housing 12.

Referring now to FIG. 2, handle assembly 10 is configured for use withsurgical instruments, especially those of the type having an elongatedistal end incorporating moving end effectors. For example, handleassembly 10 is particularly suitable for use with clip or stapleapplying surgical instruments. The inclusion of adjustableforce-limiting mechanism 30 in handle assembly 10 allows the operator topreset the maximum amount of force that can be applied by the endeffectors to a surgical clip or staple and/or to the tissue beingcompressed. Typical clip applying apparatus include drive rods whichtransfer motion from handle assembly 10 to end effectors or jaws of theclip applying surgical instrument. To accommodate the drive rod, rack 14of handle assembly 10 includes a socket 56 formed in a distal end 58 ofrack 14. Socket 56 allows rack 14 to be connected to a drive rod suchthat rack 14 can move the drive rod longitudinally within an associateddistal end portion of a surgical instrument. Socket 56 also allows thedrive rod to rotate within socket 56 as the distal end portion of thesurgical instrument is rotated relative to handle assembly 10.

To mount trigger 16 to handle assembly 12, handle assembly 12 isprovided with a mounting post 60. Trigger 16 includes a body portion 62and a finger grip portion 64 depending from body portion 62. Bodyportion 62 includes a pivot hole 66 which fits over mounting post 60 andallows trigger 16 to pivot relative to handle housing 12. A torsionspring 68 is provided to bias trigger 16 to an open position relative tohandle housing 12. Torsion spring 68 includes a central portion 70, afirst arm 72 and a second arm 74. Central portion 70 fits within bodyportion 62 of trigger 16 and over mounting post 60. First arm 72 oftorsion spring 68 engages a housing wall 76 formed on handle housing 12while second arm 74 engages an internal surface 78 of body portion 62.

As noted hereinabove, drive assembly 20 generally includes upper carrier22, pawl 24 and lower carrier 32. Upper carrier 22 includes a pair ofgrooves or slots 80 for receipt of a portion of lower carrier 32. Pinholes 82 are provided in upper carrier 22 for receipt of a pin 84 toconnect upper carrier 22 to pawl 24 as well as to secure upper carrier22 to lower carrier 32. Pawl 24 includes a pair of pivot holes 86 forreceipt of pin 84 to pivotally connect pawl 24 to upper carrier 22. Tobias pawl 24 upwardly into engagement with rack 14, drive assembly 20includes a torsion spring 88. Torsion spring 88 includes a centralportion 90, a first arm 92 and a second arm 94. Central portion 90 fitsbetween pivot holes 86 and mounts over pin 84. First arm 92 engages aninside surface of pawl 24 (not shown) while second arm 94 engages aninner surface of upper carrier 22 (not shown).

Lower carrier 32 is formed as a generally U-shaped member and includes apair of upper arms 96 which fits within slots 80 in upper carrier 22.Upper arms 96 include mounting holes 98 which align with pin holes 82 inupper carrier 22 for receipt of pin 84 to secure lower carrier 32 toupper carrier 22. Lower carrier 32 additionally includes a centralportion 100 having pivot holes 102 which are provided to rotatably mountlower carrier 32 on mounting post 60. When assembled, lower carrier 32fits within body portion 62 of trigger 16 such that torsion spring 68 ispositioned between mounting holes 102 in lower carrier 32. Lower carrier32 incorporates a pair of cut outs 46 which are configured to fit overprotrusions 48 on connecting rod 34. Cut outs 46 are formed in lowerarms 104 of lower carrier 32. It should be noted that lower arms 104 maybe sufficiently flexible relative to central portion 100 and connectingrod 34 such that lower arms 104 can flex or splay outwardly to clear cutouts 46 over protrusions 48 in connecting rod 34. In this manner, lowerarms 104 are disconnected from connecting rod 34 when handle assembly 10encounters the excessive force conditions noted above.

Handle assembly 10 includes force-limiting mechanism 30 which is able todisconnect trigger 16 from drive assembly 20 during the presence of anexcessive force condition. Force-limiting mechanism 30 is adjustable sothat the operator can preset the exact amount of force, the “break awayforce,” which will cause trigger 16 to be disconnected from driveassembly 20. Adjustable force-limiting mechanism 30 generally includesconnecting rod 34, spring 36, as well as, bushing 42 and adjustmentscrew 40. Connecting rod 34 includes an upper arm 106 having a pivothole 108 for receipt of a pin 110. Pin 110 connects upper arm 106 ofconnecting rod 34 to upper carrier 22. Specifically, upper carrier 22includes a pair of mounting holes 112 for receipt of pin 110 topivotally connect upper carrier 22 with connecting rod 34.

Connecting rod 34 includes a central portion 114 upon which are locatedat least one protrusion 48, as well as at least one ramp 50, which canconnect and disconnect connecting rod 34 to lower carrier 32 in a mannerdescribed in more detail hereinbelow. Connecting rod 34 additionallyincludes a lower arm 116 which terminates in a ball end 118. A portionof lower arm 116 and ball end 118 extends into pocket 38 formed intrigger 16 such that connecting rod 34 is constrained from movementwithin pocket 38. Ball end 118 is configured to rest against a first end120 of spring 36 such that spring 36 provides upward pressure toconnecting rod 34. A second end 122 of spring 36 is configured toreceive bushing 42 as well as adjustment screw 40. Rotation ofadjustment screw 40 causes bushing 42 to increase or decrease thecompression within spring 36.

Referring now to FIGS. 3-6, and initially with regard to FIG. 3, theoperation of handle assembly 10 incorporating adjustable force-limitingmechanism 30 is described. As noted above, handle assembly 10 isconfigured for use in various surgical instruments. Due to theadjustable nature of force-limiting mechanism 30, handle assembly 10 isparticularly suitable for use in clip or staple applying surgicalinstruments for limiting the force applied to the clip applyingmechanism, staple applying mechanism, jaw moving mechanism, etc. In theinitial position, trigger 16 is biased to an open position by torsionspring 68 relative to handle assembly 12. Pawl 24 hits wall 76 so thatpawl 24 is disengaged from rack 14. When assembled to a clip or stapleapplying distal end of portion, a firing rod 126 of the clip or stapleapplying distal end is mounted to handle assembly 10. Specifically, aproximal end 124 of firing rod 126 may be mounted within socket 56 onrack 14. A distal end of 128 of firing rod 126 extends to clip or stapleapplying and feeding mechanisms associated with the clip applying distaland portion of the surgical instrument.

As shown, in the initial position, an axis A-A is defined throughmounting post 60 and pin 84 connecting upper carrier 22 to lower carrier32. A second axis B-B is defined generally through connecting rod 34 andpin 110 joining connecting rod 34 to upper carrier 22. It should benoted that connecting rod 34 may pivot relative to upper carrier 22about pin 110. Spring 36 exerts pressure against ball end 118 ofconnecting rod 34. As noted above, prior to use, a surgeon ormanufacturer may preset the “break away force” by use of adjustmentscrew 40. In the operative condition, at least one protrusion 48 onconnecting rod 34 is firmly seated within slots 46 in lower arm 104 oflower carrier 32. In typical operation, movement of handle 16 relativeto handle assembly 12 causes lower carrier 32, connecting rod 34 andupper carrier 22 to pivot about mounting post 60 as a single connectedunit. Pivoting of upper carrier 22 about mounting post 60 moves pawl 24away from wall 76 so that pawl 24 pivots into engagement from rack 14.Pawl 24 is driven distally by the handle 16 to advance rack 14 distallywithin handle assembly 12, thereby moving firing rod 126 to actuate oneor more functions associated with the distal and portion of the surgicalinstrument.

Referring now to FIG. 4, handle assembly 10 is shown in an initialactuating condition with trigger 16 being pivoted in the direction ofarrow A. When a situation occurs in the distal end portion of theassociated surgical instrument such that rack 14 can no longer translatedistally within handle housing 12, pawl 24 is prevented from distalmovement thereby preventing upper carrier 22 and lower carrier 32 frompivoting relative to mounting post 60. In the alternative, a situationoccurs where the force applied at the handle has reached a predeterminedthreshold.

Referring now to FIGS. 4 and 5, as continued force is exerted on trigger16 in the direction of arrow A, connecting rod 34 attempts to continueto pivot about mounting post 60 relative to lower carrier 32. Becauseconnecting rod 34 is pivotally fixed relative to upper carrier 22 at pin110, connecting rod 34 is driven downwardly in the direction of arrow Bagainst the force of spring 36. The axes A-A and B-B shown in FIG. 3begin to rotate with respect to each other. Movement of connecting rod34 downwardly relative to carrier 32 forces lower arms 104 to flex orsplay outwardly such that slots 46 lift away from protrusions 48 inconnecting rod 34. With the slots 46 disconnected from protrusions 48,the connecting rod 34 can pivot with respect to lower carrier 32. Whenprotrusions 48 have become completely disconnected from slots 46 inlower arms 104, connecting rod 34 is disconnected from lower carrier 32.Trigger 16 can continue to pivot to a fully closed position as bestshown in FIG. 6.

As shown in FIG. 6, lower arms 104 are maintained in a flex outwardlycondition relative to connecting rod 34 by the presence of ramps 50 onconnecting rod 34. Once the force encountered by force-limitingmechanism 32 decreases from the “break away force,” trigger 16 may bereturned to an open position due to the bias of torsion spring 68 and/orspring 36. As trigger 16 returns to the open position, lower arms 104,which have been maintained in a flex outwardly condition by ramps 50,are allowed to reset over connecting rod 34 such that slots 46 reengageprotrusions 48 on connecting rod 34. This movement returns handleassembly 10 back to the initial operating position as shown in FIG. 3.

Thus, it can be seen that handle assembly 10 incorporating adjustableforce-limiting mechanism 30 can safely be used to actuate distal endportions of the surgical instrument while preventing the distal end ofthe instrument from exceeding excessive forces (i.e. the “break awayforce”) on tissue and/or instrument parts, and thereby prevent damage totissues and the instrument itself.

Now referring to FIGS. 7-12, there is disclosed a handle assembly 210for use with a surgical instrument. Handle assembly 210 incorporates aforce-limiting mechanism 230 to prevent excessive force applied totissue and to prevent damage to handle assembly 210 in the event of anoverload condition present at an associated end effector. Handleassembly 210 generally includes a handle housing 212 enclosing anelongated driving rack 214 mounted for longitudinal movement withinhandle housing 212. While handle assembly 210 is illustrated with onlyone half of handle housing 212 visible, one skilled in the art willappreciate that a complete and fully functional handle assembly 210 willinclude both halves of handle housing 212. Handle assembly 210additionally includes a trigger 216 movably mounted on handle housing212. Actuation of trigger 216 causes driving rack 214 to movelongitudinally within handle housing 212.

Handle housing 212 is additionally provided with a journaled noseportion 218 for rotatable support of the distal end portion of asurgical instrument. This allows end effectors associated with thedistal end portion of the surgical instrument to be rotated relative tohandle assembly 210.

To move driving rack 214, handle assembly 210 includes a drive assembly220 positioned between driving rack 214 and trigger 216. Drive assembly220 transfers motion applied to trigger 216 by an operator's hand todriving rack 214 to translate driving rack 214 longitudinally withinhandle housing 212 and thus actuate an associated end effector. Driveassembly 220 includes a carriage 222 which is mounted for movement alongwith trigger 216. A pawl 224 is pivotally connected to carriage 222 andis provided to engage driving rack 214 to move driving rack 214 withinhandle housing 212. Specifically, pawl 224 is provided with a distal lip226 which is configured to engage teeth 228 provided on driving rack214. Pawl 224 is spring biased into engagement with driving rack 214. Asnoted hereinbelow, teeth 228 are oriented such that distal lip 226 canengage teeth 228 and move driving rack 214 distally within handlehousing 212 when pawl 224 is moved in the distal direction and disengagefrom driving rack 214 as pawl 224 is drawn in a proximal directionrelative to driving rack 214.

As noted hereinabove, handle assembly 210 includes a force-limitingmechanism 230 which is provided to disengage trigger 216 from driveassembly 220, and thus from driving rack 214, when force-limitingmechanism 230 encounters a predetermined amount of force present betweendrive assembly 220 and trigger 216. This may occur in a situation wherean end effector encounters sufficiently stiff or tough materials suchthat continued actuation of the surgical instrument will result indamage to the surgical instrument or to tissue. Additionally, theexcessive force condition may occur in the event of damage to theassociated end effector thereby preventing driving rack 214 fromtranslating longitudinally within handle housing 212.

In a particular application, the excessive force condition can be presetduring configuration of handle assembly 210 such that an end effectorassociated with handle assembly 210 may only apply a force up to apredetermined force to the tissue being operated upon. Once thepredetermined force has been reached, force-limiting mechanism 30enables trigger 216 to be disengaged from drive assembly 220 therebypreventing an excessive amount of force being applied to tissue.

Force-limiting mechanism 230 includes a plunger 232 which is movablymounted on trigger 216. Plunger 232 is configured to engage carriage 222and transfer the motion of trigger 216 to carriage 222, and thus to pawl224, to translate rack 214 within handle housing 212. Force-limitingmechanism 230 operates to disengage trigger 216 from carriage 222 bydisengaging plunger 232 from carriage 222 in response to a predeterminedforce existing between carriage 222 and plunger 232.

As noted hereinabove, rack 214 is mounted for longitudinal movementwithin handle housing 212. Rack 214 includes a rack lip 234 which ridesalong a longitudinal housing rail 236 provided on handle housing 212.While rack 214 is disclosed as moving along housing rail 236, othermeans of supporting rack 214 for longitudinal movement within handlehousing 212 may alternatively be provided, such as, for example,grooves, tracks, or other methods of longitudinally supporting rack 214for movement within handle housing 212.

Referring to FIG. 8, the components of handle assembly 210 are describedin detail. As noted above, handle assembly 210 is configured for usewith the distal end section of various surgical instruments whichincorporate movable end effectors. Rack 214 of handle assembly 210 isprovided with a socket 238 formed on a distal end 240 of rack 214.Socket 238 may be configured to receive a driving or motion rodassociated with the distal end components of a surgical instrument.While rack 214 is illustrated as having socket 238, other means ofconnecting rack 214 to the movable components of a distal end of asurgical instrument are also contemplated herein.

To allow trigger 216 to move relative to handle housing 212, handlehousing 212 is provided with a mounting post 242 which serves as a pivotpoint for both trigger 216 and carriage 222 in a manner described inmore detail hereinbelow. Trigger 216 is provided with a body portion 244and an open finger portion 246 depending from body portion 244. Bodyportion 244 includes a pivot hole 248 which fits over mounting post 242on handle housing 212. A torsion spring 250 is provided between handlehousing 212 and trigger 216 to bias trigger 216 into a distal most oropen position. Torsion spring 250 includes a central portion 252, afirst arm 254 and a second arm 256. Torsion spring 250 fits within acentral slot or cavity 258 formed in body portion 244 of trigger 216.Central portion 252 fits over mounting post 242 and first arm 254 restsagainst a housing wall 260 formed handle housing 212. Second arm 256 oftorsion spring 250 engages a proximal tab 262 formed on body portion 244to bias trigger 216 into the open position.

Body portion 244 of trigger 216 additionally includes a forward tab 264for engagement with carriage 222 to move carriage 222 proximallyrelative to rack 214. Body portion 244 further includes a plunger pocket266 for receipt of plunger 232 to allow plunger 232 to move into and outof engagement with carriage 222 in a manner described in more detailhereinbelow.

With reference to FIG. 8, carriage 222 generally includes a lowerportion 268 having a mounting hole 270. Lower portion 268 fits withincavity 258 formed in trigger 216 such that mounting hole 270 fits overmounting post 242. Thus, carriage 222 pivots about a common axis withbody portion 244 of trigger 216. Carriage 222 additionally includes apartially sectioned or split upper portion 272 having a pair of mountingholes 274. A pivot pin 276 is provided through mounting holes 274 toattach pawl 224 to carriage 222. This enables pawl 224 to be drivenlongitudinally by movement of carriage 222, as well as allowing pawl 224to pivot relative to carriage 222.

Carriage 222 additionally includes an undercut or arcuate surface 278 sothat trigger 216 may pivot relative to carriage 222 when force-limitingmechanism 230 disengages trigger 216 from carriage 222. Carriage 222 isprovided with an angled surface 280 which is configured to releasablyengage a corresponding surface on plunger 232 of force-limitingmechanism 230. Trigger 216 is provided with a corresponding arcuatesurface 282 so that trigger 216 can pivot independently of carriage 222.Upper portion 272 of carriage 222 includes a leading edge 284 which isengaged by a front edge 259 of slot 258 so as to rotate carriage 222clockwise, in response to release of trigger 216, and thus draw pawl 224proximally within handle housing 212.

Pawl 224 is formed as a generally U-shaped or saddle member having apair of mounting holes 286. Pawl 224 is pivotally connected to carriage222 by insertion of pin 276 through mounting holes 286. Drive assembly220 additionally includes a torsion spring 288 for biasing pawl 224 intoengagement with rack 214. Specifically, torsion spring 288 includes acentral portion 290, a first arm 292 and a second arm 294. Centralportion 290 fits over and is supported by pin 276 and first arm 292rests against a surface 296 formed on carriage 222. Second arm 294engages an underside pawl surface 298 of pawl 224 to bias pawl 224upward into engagement with rack 214.

As noted hereinabove, handle assembly 210 incorporates a force-limitingmechanism 230 which enables trigger 216 to be disengaged from driveassembly 220 when drive assembly 220 is prevented from moving due tofactors including the inability of rack 214 to move. Force-limitingmechanism 230 generally includes plunger 232 and a pair of springs 306,which are located within plunger pocket 266 and beneath plunger 232, tobias plunger 232 upwardly into engagement with carriage 222.

With reference to FIG. 10, plunger 232 includes an angled surface 300which is configured to engage angled face 280 on carriage 222.Engagement of angled surface 300 with angled face 280 allows trigger 216to be connected to carriage 222 and pivot carriage 222 as trigger 216 isactuated. As shown, plunger 232 additionally includes a relatively flatsurface 302 which rests against arcuate surface 278 of carriage 222 andprevents plunger 232 from springing out of plunger pocket 266 andtrigger 216. In one embodiment, plunger 232 is formed with a plungerpocket 304 (FIG. 8) for receipt of a portion of springs 306.

The amount of force encountered by plunger 232 such that plunger 232disconnects from carriage 222 may be preset in at least two differentways. First, angled face 280 and angled surface 300 may be formed todefine a predetermined coefficient of friction therebetween. This will,in part, determine the amount of force necessary for angled surface 300to slip relative to angled face 280 and allow plunger 232 to be forceddownwardly within plunger pocket 266 and disengage from carriage 222.Second, the force of springs 306 may be chosen to determine the forcenecessary to urge plunger 232 downwardly within plunger pocket 266 andthereby disengage plunger 232 from carriage 222. The angle of angledsurface 300 and angled face 280 can be chosen to affect thepredetermined amount of force. It should be noted that, whileforce-limiting mechanism 230 is illustrated as utilizing two springs306, any number of springs, as well as other forms of springs, may beutilized to urge plunger 232 into engagement with carriage 222. Third,an adjustment spring 235 (FIG. 10) may be included to facilitateadjustment of spring force.

Referring now to FIGS. 9-12, and initially with respect to FIG. 9, theoperation of handle assembly 210 to advance to rack 214 within handlehousing 212 is described. As shown, in an initial position, rack 214 isin a proximal most position within handle housing 212 and trigger 216 isbiased to an open or distal most position by torsion spring 250. Plunger232 of force-limiting mechanism 230 is engaged with carriage 222allowing carriage 222 to pivot about common axis on mounting post 242with trigger 216. Pawl 224 is urged upwardly due to the bias of torsionspring 288 (FIG. 8) urging distal lip 226 of pawl 224 into engagementwith teeth 228 of rack 214.

Referring now to FIG. 10, as trigger 216 is squeezed or moved proximallyrelative to handle housing 212, body portion 244 of trigger 216 rotatesin a counterclockwise fashion about mounting post 242. Carriage 222pivots commonly about mounting post 242 with body portion 244. As notedhereinabove, angled face 280 of carriage 222 is in engagement withangled surface 300 of plunger 232 maintaining the connection betweencarriage 222 and trigger 216. As carriage 222 pivots about mounting post242, it drives pawl 224 distally thereby driving rack 214 distally inresponse to the engagement of distal lip 226 with teeth 228.

As is common with rack and pawl engagement systems, rack teeth 228include relatively flat driving surfaces 308 which are configured to beengaged with distal lip 226 of pawl 224 so that pawl 224 can drive rack214 longitudinally. Rack teeth 228 additionally include angled or slopedsurfaces 310. Sloped surfaces 310 allow pawl 224 to moved proximallyrelative to rack 214 such that distal lip 226 rides over angled surfaces310 and moves downwardly against the bias of torsion spring 288. Thisallows pawl 224 to be drawn proximally back to a new position so thattrigger 216 may be actuated to again drive rack 214 a farther amountdistally.

Referring now to FIG. 11, as noted hereinabove, handle assembly 210 isprovided with force-limiting mechanism 230 which prevents damage totissue due to excessive forces applied to the tissue by an end effectorassociated with handle assembly 210, as well as preventing damage tohandle assembly 210 and an associated end effector in the eventcomponents of the surgical instrument become damaged during use. Thisoccurs when rack 214 encounters excessive resistance against distalmotion within handle housing 212. When this occurs, the resistance forceencountered by a rack 214 is transmitted through pawl 224 to carriage222. When the resistance encountered by carriage 222 rises to apredetermined amount, angled surface 300 of plunger 232 begins to sliprelative to angled face 280 of carriage 222. Plunger 232 is forceddownwardly within plunger pocket 266 against the bias of springs 306. Asnoted hereinabove, the force necessary to move plunger 232 downwardlywithin pocket 166 is determined by the coefficient of friction presentbetween angled face 280 of carriage 222, the component of the frictionforce acting generally downwardly against the spring or springs 306, andangled surface 300 of plunger 232 and the predetermined resistance forcepresent in springs 306. As shown, as plunger 232 moves downwardly withinplunger pocket 266, body portion 244 of trigger 216 continues to rotatecounterclockwise causing forward tab 264 of body portion 244 to separatefrom leading edge 284 of carriage 222. Because arcuate surface 278 ofcarriage 222 has approximately the same radius as arcuate surface 282 ofbody portion 244, trigger 216 may continue to pivot about mounting post242 while carriage 222 remains stationary. Handle assembly 210 mayinclude a stop or other mechanism for maintaining the position of rack214 when force-limiting mechanism 230 releases trigger 216.

As best shown in FIG. 12, once plunger 232 has moved completelydownwardly within plunger pocket 266, plunger 232 is disconnected fromcarriage 222, thus allowing body portion 244 of trigger 216 to freelyrotate without imparting any force to carriage 222, and thus to pawl 224and rack 214. While not specifically shown in this embodiment, uponrelease of trigger 216 against the bias of torsion spring 250 (FIG. 8)body portion 244 will rotate clockwise bringing forward slot 254 of bodyportion 244 into engagement with leading edge 284 of carriage 222. Thisallows trigger 216 to drive carriage 222, and thus pawl 224, proximallyrelative to rack 214 to reset for further actuation of trigger 216.

In this manner, force-limiting mechanism 230 allows handle assembly 210to be actuated and operate an associated distal end effector withoutdamage to tissue or the internal components of a surgical instrumentconsisting of handle assembly 210 and an associated distal end portion.By choosing the appropriate strength for springs 306 and/or designingthe predetermined coefficient of friction and angle for angled face 280and angled surface 300, the maximum force applied to tissue, as well asthe internal components of handle assembly 210, can be predetermined.

It will be understood that various modifications may be made to theembodiment disclosed herein. For example, different types of springs maybe substituted for the coil springs illustrated to bias the discloseclutch mechanism into the drive assembly. Further, the composition andorientation of the disclose clutch components may be altered to engagethe drive assembly in differing manners. Additionally, the discloseddrive assembly need not necessarily include a rack and pawl system butmay be substituted for other drive systems such as, for example, gears,motor-driven systems, etc. The force-limiting mechanism may include anadjustment mechanism for adjusting the threshold force for theforce-limiting mechanism. The force-limiting mechanism may be providedin handle assemblies for graspers, clip appliers, staplers, surgicalinstruments for applying energy to tissue, or other instruments.Therefore, the above description should not be construed as limiting,but merely as exemplifications of a particular embodiment. Those skilledin the art will envision other modifications within the scope and spiritof the claims appended hereto.

The invention claimed is:
 1. A handle assembly for use with a surgicalinstrument having an operative distal end portion comprising: a handlehousing; a drive element movably mounted within the handle housing andconnected to an operative distal end portion for performing surgery; anactuator movably mounted on the handle housing; and a force-limitingmechanism disposed between the drive element and the actuator, theforce-limiting mechanism having a breakaway force, the force-limitingmechanism including: a carriage in mechanical cooperation with theactuator; a pawl pivotably connected to the carriage; a plunger slidablyconnected to the actuator; wherein the carriage includes an angledsurface for engaging at least a portion of the plunger; theforce-limiting mechanism being attached to the actuator so that theforce-limiting mechanism moves with the actuator when the force appliedto the actuator is less than the breakaway force and so that theforce-limiting mechanism pivots with respect to the actuator when theforce applied to the actuator meets the breakaway force, theforce-limiting mechanism applying a drive force to the drive elementwhen the force applied to the actuator is less than the breakaway force.2. The handle assembly as recited in claim 1, wherein the force-limitingmechanism includes a lower carrier.
 3. The handle assembly as recited inclaim 2, wherein the force-limiting mechanism includes a connecting rodconnected to the actuator and releasably connected to the lower carrier.4. The handle assembly as recited in claim 3, wherein the connecting rodis slidably disposed in the actuator and a spring is positioned betweenthe actuator and the connecting rod.
 5. The handle assembly as recitedin claim 4, wherein the lower carrier is pivotably connected to theactuator.
 6. The handle assembly as recited in claim 5, wherein thelower carrier is pivotably connected to an upper carrier, the uppercarrier being pivotably connected to the connecting rod.
 7. The handleassembly as recited in claim 2, wherein the drive element comprises arack having at least one tooth and further comprising a pawl pivotablyconnected to the force-limiting mechanism for engagement with the rack.8. The handle assembly as recited in claim 1, wherein the plunger isslidably disposed at least partially within the actuator.
 9. The handleassembly as recited in claim 8, wherein at least one spring is disposedbetween the plunger and the actuator.
 10. The handle assembly as recitedin claim 1, wherein the plunger includes an angled face for engaging theangled surface, the angled surface and angled face being arranged sothat the carriage is able to depress the plunger.
 11. The handleassembly as recited in claim 10, wherein the plunger is biased towardthe carriage with a predetermined amount of force.